Quantitation of secretion by rat basophilic leukemia cells by measurements of quinacrine uptake

A novel method for quantitating secretion is described based on measurements of the cellular uptake of the fluorescent aminoacridine dye quinacrine into low-pH secretory granules. The quinacrine fluorescence remaining in the medium was found to decrease after incubation with increasing numbers of the 2H3 rat basophilic leukemia line. This depletion of dye from the medium decreased after a secretory stimulus. Assuming that quinacrine partitions according to mass action, a quantitative model was derived to allow calculation of the percent secretion from dye uptake data. A good correlation was obtained when the values for the percent secretion determined by the quinacrine uptake method were compared with secretion measured by release of the granule enzyme beta-glucuronidase.